GB458028A - Improvements in the manufacture and production of water-soluble condensation products having tanning action - Google Patents

Abstract

Tanning-agents are prepared by condensing with formaldehyde and aromatic sulphonic acids, products obtained from insoluble substances having at least one phenolic hydroxy group and formaldehyde-bisulphite or formaldehyde and sulphurous acid salts. The tanning agents also have plumping action and may be used, after acidification with, for example, formic or sulphuric acid, for tanning reptile skins, unhaired hides or upper leathers. In modifications of the process of manufacture, (a) aromatic carboxylic acids are used instead of aromatic sulphonic acids; (b) hydroxy compounds of the benzene or naphthalene series are used with the aromatic sulphonic acids; (c) the products are further treated with urea and formaldehyde. In examples: (1) the product obtained by reacting together formaldehyde, calcined sodium sulphite and 4 : 4<1>-dihydroxydiphenylsulphone is condensed with formaldehyde and cresolsulphonic acid, b : b -di(4-hydroxyphenyl)propanesulphonic acid, a formaldehyde-cresolsulphonic acid condensation product, a formaldehyde-naphthalene sulphonic acid condensation product, a formaldehydecresolsulphonic acid condensation product together with cresol, b : b -di(4-hydroxyphenyl)-propane, or together with cresol and dihydroxydiphenylsulphone and b : b - di(4 - hydroxyphenyl)propanedisulphonic acid together with b : b -di(4-hydroxyphenyl)propane; (2) the product obtained by reacting together formaldehyde, calcined sodium sulphite and 4 : 4<1>-dihydroxy - 3 : 3<1> - dimethyldiphenylsulphone is condensed with formaldehyde and o-hydroxybenzoic acid; (3) the product obtained by reacting together formaldehyde, sodium sulphite and 4 : 4<1> - dihydroxy - 2 : 2<1> - dimethyldiphenylsulphone is condensed with formaldehyde and phthalic acid; (4) a product obtained by reacting together formaldehyde-bisulphite and humic acid is condensed with a formaldehyde-naphthalenesulphonic acid condensation product or a formaldehyde cresol sulphonic acid condensation product together with cresol or naphthol. Insoluble condensation products containing a phenolic hydroxy group obtained from phenol and formaldehyde, b : b -di(4-hydroxyphenyl)propane and humous coal may be reacted with formaldehydebisulphite and used as starting material. Condensation products of phenol, cresols and xylenols with aldehydes and ketones, dihydroxydiarylmethanes and dihydroxy diarylsulphides are also examples of insoluble phenolic compounds which may be used. The following aromatic sulphonic acids are mentioned: naphthalene mono and polysulphonic acids, chlorcresolsulphonic acids, sulphanilic acid, naphthylaminosulphonic acids and chlornaphthalenesulphonic acids. 4-Chlor-2-hydroxybenzoic acid, terephthalic acid, naphthalic acid and 2 : 2<1>-dihydroxydiphenyl methane-4 : 4<1>-dicarboxylic acid are specified carboxylic acids. According to the Provisional Specification any aldehyde or ketone of low molecular weight may replace the formaldehyde.